An important quality feature of a digital/analog converter (DAC) is its resolution. However, the resolution also makes a significant contribution to the manufacturing costs of a digital/analog converter. For this reason, it is an aim, when developing digital/analog converters, to attain a high resolution with a small number of components required for this and with a small area requirement for implementation in an integrated circuit. In addition, the digital/analog converter's power loss in operation needs to be as low as possible.
One class of known digital/analog converters comprises binary-weighted digital/analog converters. By way of example, these can be based on R-2R networks. Such digital/analog converters are distinguished by a particularly small number of components. However, very high demands need to be placed on the equality of the individual resistors in order to avoid nonlinearities. This necessitates a large area requirement in an integrated circuit. Furthermore, it is sometimes necessary to calibrate the resistors in the R-2R network.
Another class of known digital/analog converters contains segmented digital/analog converters. By way of example, segmented digital/analog converters are based on of 2resolution−1 equal resistors, with the resolution of the segmented digital/analog converter in question being specified in bits. Segmented digital/analog converters have a very high differential linearity and guaranteed monotony of the characteristic. A drawback of segmented digital/analog converters is the very large number of resistors required and an area requirement which grows exponentially with the resolution. For this reason, segmented digital/analog converters are not suitable for use to attain a high resolution.
In addition, it is known practice to increase the resolution of a digital/analog converter using digital signal processing, for example using noise shapers. Such digital signal processing is very complex, however. Noise shapers also have the drawback that their limit cycles can cause unwanted interference signals. In addition, the quantization noise subjected to high-pass filtering by the noise shaper requires subsequent analog low-pass filtering of the output signal. In this case, the analog low-pass filter needs to have a high degree of linearity so that the high-pass filtered quantization noise is not transformed to the useful band through intermodulation. Another drawback of noise shapers is additional power loss caused both by the noise shaper and by the analog low-pass filter.